Grid controlled gaseous discharge tube



Nov. 20, 1962 P. w. STUTSMAN 3,065,3 72

GRID CONTROLLED GASEOUS DISCHARGE TUBE Filed Aug. 23, 1949 3Sheets-Sheet 1 SIGNAL INPUT P. W. STUTSMAN GRID CONTROLLED GASEOUSDISCHARGE TUBE Nov. 20, 1962 3 Sheets-Sheet 2 Filed Aug. 23, 1949 PELHYCOIL d w d M w M M L 6 a 2 w w a PM P 0/ a 1 Q H Q; W J m 6 T 6 mnl 4flu 52g v. R 1 I II I III 1 1/ 1 I I 2% 5 5525 5 5 a M 3 mum INVENTOR5'7UT5'MAN ATTORNEY Nov. 20, 1962 P. w. STUTSMAN 3,065,372

GRID CONTROLLED GASEOUS DISCHARGE TUBE Filed Aug. 23, 1949 5Sheets-Sheet 3 H it 59 *72 73 50 v 1- I? 239 l INVE/V 70/? P1901. WSTUTSMfl/V United States Patent ice 3,065,372 GRID CDNTRQLLED GASEOUSDISCHARGE TUBE Paul W. Stutsinan, Needlram, Mass, assignor to RaytheonCompany, Lexington, Mass, a corporation of Delaware Filed Aug. 23, 1949,Ser. No. 111,874 12 Claims. (Cl. 313197) This application rel-ates togaseous discharge devices and more particularly to gaseous dischargedevices of the grid control type capable of passing high peak currents.

Prior gas discharge devices, capable of passing relatively large peakcurrents such as, for example, the OA4G and the 1021, have a useful lifethat is relatively short due to depletion of electron emissive materialfrom the cathode surface. In order to lengthen the useful life of gastubes of this general class applicant has provided a cathode comprisinga hollow cylinder coated with electron emissive material on its innersurface whereby emissive material sputtered off from the inner wall ofthe cathode cylinder will usually remain inside the cylinder andredeposit on another part of the wall. The use of this type cathodecreates the problem of utilizing this type cathode in a cold cathode gasdischarge device which may be triggered by relatively low grid inputsignals. In applicants device a keep-alive discharge of, for example, 1milliampere is maintained between the cathode and a keep-alive electrodepositioned between the cathode and the anode. Electrons may then bedrawn from this keep-alive discharge by a relatively low positivepotential on the control grid, the electrons passing through the controlgrid being accelerated to the anode to initiate firing of the device.For example, a peak grid voltage of 20 volts is suflicient to reliablyfire the tube. In addition, by adequately shielding the anode from thecathode a relatively forward large voltage may be applied between theanode and cathode, for example, several hundred volts without firing thetube in the absence of an input signal to the control grid.

In a species of the invention illustrated herein applicant providesmeans whereby the voltage required to initiate keep-alive discharge ismaterially lowered. To accomplish this a starter electrode is made inthe form of a U-shaped wire which is inserted into the hollow interiorof the cathode thus bringing the starter electrode in close proximitywith the electron emissive surface of the cathode. Due to the closeproximity of the starter electrode to the emissive surface of thecathode a relatively low voltage, for example, 110 volts will initiate adischarge, this discharge being then transferred to the keepaliveelectrode.

Applicant further provides circuits particularly adapted to utilize thevarious species of the tubes illustrated herein. Particularly, applicantprovides a circuit wherein relaxation oscillations take place in thestarter electrode discharge circuit whereby there occurs a resultantdiffusion of ions away from the plasma, some toward the keepaliveelectrode. In this manner the discharge extends to the keep aliveelectrode whence the keep-alive current increases and more electronsbecome available upon which the control grid may act to fire the tube.

Thus it may be seen that applicant has provided herein a dischargedevice having extremely long life due to the sputter conservationconstruction of the cathode, a relatively low grid firing volt-age dueto a keep-alive discharge, said device being incorporated in asubminiature tube which is more sensitive, versatile and rugged, andcapable of handling larger peak currents than prior discharge devices ofthis type.

The particular manner whereby the aforementioned spirally wrapped aroundanode rod 26. Anode rod 26; is then joined, for example, by welding to alead-in wire- 3,065,372 Patented Nov. 20, 1962 advantages areaccomplished will now be described in detail reference being had to thedrawings wherein:

FIG. 1 illustrates a longitudinal cross-sectional view of one species ofthe discharge device taken along line 11 of FIG. 2;

FIG. 2 illustrates a transverse cross-sectional view of, the speciesshown in FIG. 1 taken along line 2-2 of FIG. 1;

FIG. 3 illustrates a circuit adapted to utilize the discharge device ofFIGS. 1 and 2;

FIG. 4 illustrates a longitudinal cross-sectional view of anotherspecies of the discharge device taken along line 4-4 of FIG. 5;

FIG. 5 illustrates a transverse cross-sectional view of the speciesshown in FIG. 4 taken along line 5-5 of FIG. 4;

FIG. 6 illustrates a circuit adapted to utilize the dis-' the speciesshown in FIG. 7 taken along line 8-8 of FIG.

7; and

FIG. 9 illustrates a circuit adapted to utilize the discharge device ofFIGS. 7 and 8.

Referring now to FIG. 1, there is shown a glass envelope 20 consistingof a tube, one end of which is pressed together as at 21 and throughwhich extenda plurality of lead-in wires. The other end of the glasstube 20 is curved together and contains at its center a mass of glass 22which is used to seal the envelope aft-er filling of the envelope withthe correct gaseous medium. Extending upward from the glass press 21inside envelope 20 are three glass tubes 23, 24 and 25 whose axes areall parallel and lying in the same plane and spaced an equal distanceapart. The center glass tube '24 extends approximately.

one-third the length of envelope 20. Inside the glass.

tube 24 which is hollow, is an anode rod 26 which ex,

tends from the open end of the glass rod 24 toward the; glass press 21through a spacer 27 consisting of a wire;

28 which extends through the glass press 21.

The end of the tube 24 which is open, is covered by a cup-shaped grid 29of wire mesh which may be made of 60 x 60 strands per inch screeningusing .005 inch nickel wire. The diameter of the cup-shaped grid 29 isslightly larger than the diameter of the glass tube 24 and extends forsomewhat more than one diameter of the glass tube over the end of saidrod. The bottom of said cupshaped grid 29 is in close proximity but nottouching the end of the tube 24 and the anode element 26. Cup

shaped grid 29 is supported by being attached as by welding to a strap30 at the lip of said cup-shaped grid. The strap 30 extends around thetubes 23- and 25 thereby rigidly supporting the grid 29. The tubes 23and 25 are somewhat longer than the tube 24 and extend further into theenvelope 20 past the end of tube 24 and the grid 29. A lead-in wire 31is attached to the strap 30 as by Welding and extends along the side ofenvelope 20 through the glass press 21.

Surrounding the grid 29 is a second cup-shaped grid 32 which is similarin shape to grid 29 but somewhat larger in diameter. The second grid 32is supported by a strap 33 placed around the rods 23 and 25 similar tothat supporting grid 29. A lead-in member 34 attached along the rods 23and 25 with the result that the grid 32 3 is insulated from the grid 29.The glass rods 23 and 25 extend slightly beyond the bottom of cup-shapedgrid 32.

Extending the length of rods 23 and 25 which are hollow, are a pair ofsupport rods 35 which are butt welded to lead-in members 36 extendingthrough the glass press 21. The rods 35 have spacers 37 thereon similarto the spacer 27 on anode rod 26. The rods 35 extend out of the openends of the glass rods 23 and 25 for a distance equal to approximatelythe diameter of envelope 20, said rods passing through a mica plate 38.The mica plate 38 is flat and has a shape conforming to the insidecontour of the envelope 20 at a section taken at the right angles to therods 35. The mica support member 38 has a hole therein approximatelyequal in diameter to and concentric with the inside diameter of theglass anode shielding tube 24. A second mica member 40 similar in shapeto the mica member 38 and having a hole therein similar to the hole inmica member 38 and concentric therewith, is positioned parallel with themember 38 and spaced slightly therefrom on the opposite side of member33 from the grid 32. Between mica members 38 and 40 is positioned aflat, mesh grid 41 completely covering the holes in mica members 38 and40, said grid being attached to a lead-in member 39 which passes downthrough envelope 20 and press 2 1.

Above mica member 40 is a cathode 42 comprising a metallic cylinder 43which may be, for example, of nickel whose diameter is somewhat smallerthan the diameter of envelope 20 and whose length is somewhat greaterthan its diameter. The lower end of the cylinder 43 rests on the micamember 40 and has attached thereto an end plate 44 which may be ofnickel and which has a hole 45 therein, concentric with the holes inmica members 38 and 40, and whose diameter is somewhat less than theinside diameter of the rod '24. The upper end of the cylinder 43 issealed by a second end plate 46. The upper end of the cylinder 40 restsagainst a mica member 47 similar to member 40 but having no holetherein. Inside the cylinder 43 is wound a wire 48 which containselectron emissive material said wire completely covering the inside ofcylinder 43. The lower end of the cathode 42 is supported by the rods 35which extend through the bottom plate 44 of the cathode 42 just insidethe cylinder 43 and wire winding 48 for approximately half the length ofthe cylinder 43 and are rigidly attached to the end plate 44 and thewire 48.

Referring now to FIG. 3 there is shown a circuit diagram utilizing thespecies of the device shown in FIGS. 1 and 2. The cathode 42 isconnected to ground. The anode is connected to a positive voltage sourcethrough load 49. Grid 29 adjacent the anode 26 is connected to B+through three series resistors 52, 53 and 54 which may be 3 megohms, 1megohm, and 100 kilohms respectively. Grid 29 is also connected tosource of signals through a DC. blocking condenser 50. The grid 32 isconnected to the junction between resistors 53 and 54. The grid 41 whichacts as the keep-alive grid, is connected to the junction between theresistors 52 and 53.

In the absence of a signal on grid 29 keep-alive current flows from thecathode to the keep-alive grid in the form of a glow discharge. Theapplication of a signal to grid 29 draws electrons from the keep-alivestream of electrons through shielding grid 32 whereupon they are drawnto the anode 26 creating positive ions by collision with gas molecules.These positive ions bombard cathode 42 creating a suflicient supply ofelectrons for an arc discharge of the tube through the load 49 which maybe, for example, a relay coil.

' Referring now to FIGS. 4 and 5, there is shown a modification of thedevice of 'FIGS. 1 and 2, like elements of the species having likereference numerals. This device issimilar to the species of FIGS. 1 and2 except that another electrode 55 has been added which acts as astarter electrode. This electrode 55 comprises a piece of wire bent in aU-shape, said U-shape section extending into the cathode through thehole 45 for a distance approximately equal to the diameter of said hole.The legs of the U extend downward through the hole and their ends arebent at right angles outwardly. These bent ends rest on and are firmlyattached to a metallic ring 56 surrounding the hole in the mica spacer49. Lying on top of said metallic ring 56 firmly pushing the ring 56 andthe bent ends of the U-shaped member 55 against the mica spacer 40 isanother mica spacer 57 similar to the mica spacer 40. The mica spacer 57is spaced from the cathode 42 by two heads 58 surrounding the rods 35and positioned between the bottom of the cathode 42 and the mica spacer57.

The U-shaped member 55 has one of its ends connected to a lead-in member59 which extends along the side of envelope 2% through the glass press21 at the bottom of the tube. The U-shaped member 55 does not touch thecathode 42 as it passes through the hole in base member 44. Attached tothe top of cathode 42 is a getter support 44 containing getter materialin detents therein.

By applying a suitable potential between the member 55 and the cathode42 a glow discharge current is caused to flow between the cathode 42 andthe member 55. Since the U-shaped member 55 extends into the cathodecylinder 43 it is possible to initiate this keep-alive discharge betweenthe cathode 42 and the grid 55, with a relatively low voltage. Thedischarge between grid 55 and cathode 42 may then be extended to thekeep-alive grid 41 thereby creating the keep-alive discharge on whichthe control grid may act.

Referring now to FIG. 6, there is shown a circuit utilizing this speciesof the device. The anode circuit is similar to that of FIG. 3, and thecathode 42 is grounded. The starter electrode 55 is connected to B+through a resistor 63 of, for example, 1 megohm which is bypassed by acondenser 61 of, for example, .002 microfarad thereby maintaining asubstantially constant keep-alive voltage between the cathode 42 andgrid 55 during firing of the tube. Grid 41 is connected to B-lthroughresistor 62 of, for example, 2 megohms which is bypassed by a condenser63 of, for example, .002 microfarad to maintain the voltage on thekeep-alive grid constant during tube discharge. The grid 32 is connectedto B+ through a resistor 64 which may be, for example, .5 megohmby-passed by a 5 micro-microfarad condenser 65. Grid 29 is connected togrid 32 through a grid load resistor 66 of, for example, 3 megohms andto a source of signals through a DC. blocking condenser 50.

The electron emissive wire 43 has been omitted from the inside of thecathode cylinder 43 and electron emissive material is coated directly onthe inside of the cylinder 43.

Due to relaxation oscillations in the plasma between the starterelectrode and the cathode, which are not damped by the external circuit,ions are diffused from this discharge, some moving toward the keep-alivegrid 41 thus these ions by bombardment of gas molecules create electronswhich are attracted to the grid 41 thus extending the discharge thereto.A signal applied to grid 29 attracts electrons from the glow dischargebetween grid 41 and cathode 42 through the grid 32 to the anode 26 thusfiring the tube by the action previously described.

Referring now to FIGS. 7 and 8, there is shown a modification of thespecies described in FIGS. 4 and 5 wherein cup-shaped grids 29 and 32have been replaced by fiat grids. In this device the cathode 42, grids55 and 41, and mica spacers 38, 43 and 57 and the supports therefor aresimilar to those shown in FIGS. 4 and 5.

Below spacer 38 is a grid 67 similar to grid 41 which is attached tolead-in 34 extending through the glass press 21. Below grid 67 is a micaspacer 68 similar to spacer 38. Beneath mica spacer 68 is another grid69 similar to grids 41 and 67 and attached to the lead-in member 31.Beneath grid 69 is a mica spacer 70 similar to the mica spacer-s 33 and68 but having a somewhat larger hole therein. Beneath the mica spacer 70is a metallic plate 71 slightly larger in diameter than the hole inspacer 7t) and covering the bottom of said hole. This metallic plate 71which constitutes the anode, is attached to the anode rod 26 whichextends slightly beyond the end of the anode sleeve 24. Beneath theplate 71 is a mica spacer 72 surrounding the anode rod 26 and restingagainst the end of anode insulating sleeve 24 thus holding the variouslayers of the aforementioned grid and mica spacer assembly firmlypressed together. Resting on the ends of the glass tubes 23 and 25 is amica spacer 73 similar to spacer 72 whose purpose is to maintain therelative position of the various lead-in wires.

By using flat grids rather than basket-shaped grids, the anode andcathode may be spaced somewhat closer together thus decreasing the anodedrop during discharge and in addition simplifying the fabrication of thegrids.

Referring now to FIG. 9, there is shown a circuit diagram which may beused in conjunction with the species shown in FIGS. 7 and 8. In thiscircuit the cathode 42 is connected to ground, and the anode circuit issimilar to those previously described. The starter electrode 55 isconnected to 13+ through a 2 megohm resistor 74, and to ground through acondenser 78 of, for example, .005 microfarad. Grid 41 is connected togrid 69 and to B+ through a resistor 75 of .066 megohm and to groundthrough a tapped resistor 7 6 which may be, for example, 2 /2 megohms.Grid '67 is connected to the tap on resistor '76 through a grid loadresistor 77 of 3 megohms and to a signal input through a DC. blockingcondenser 50.

This completes the description of the specific embodimerits illustratedherein. However, modifications will be apparent to persons skilled inthe art, for example, the discharge between anode and cathode may be inthe form of a glow discharge, rather than an arc discharge, and therelay coil could be put between cathode and ground rather than in theanode circuit. Therefore, applicant does not wish to be limited to theparticular details of the modifications described herein except asdefined by the appended claims.

What is claimed is:

1. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode positioned outside saidcathode and a starter electrode extending inside said cathode, saidstarter electrode being substantially surrounded by theelectron-emissive surface of said cathode.

2. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode positioned outside saidcathode coaxial with said cathode and spaced therefrom longitudinallyalong the axis thereof, and a starter electrode extending inside saidcathode, said starter electrode comprising a U-shaped wire and beingsubstantially surrounded by the electronemissive surface of saidcathode.

3. An electron discharge device comprising an envelope containing agaseous medium, a cathode comprising a hollow cylinder having its innersurface substantially entirely coated with electron emissive material,an anode positioned outside said cathode, and a starter electrodeextending inside said cathode, said starter electrode comprising aU-shaped wire substantially entirely surrounded by the electron-emissivesurface of said cathode.

4. An electron discharge device comprising an envelope containing agaseous medium, a cathode comprising a cylinder having its inner surfacecoated with electron emissive material, an anode positioned outside saidcathode and surrounded by a sleeve of insulating material, a gridsubstantially covering the exposed end of said insulating sleeve andshielding said anode, and a keep-alive grid positioned adjacent saidcathode.

5. An electron discharge device comprising an envelope containing agaseous medium, a cathode comprising a cylinder having its inner surfacecoated with electron emissive material, an anode positioned outside saidcathode and surrounded by a sleeve of insulating material, a gridsubstantially covering the exposed end of said insulating sleeve andshielding said anode, and a starter electrode extending inside saidcathode, said starter electrode comprising a U-shaped wire.

6. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode surrounded by a sleeve ofinsulating material, a first grid substantially covering the end of saidinsulating sleeve and shielding said anode, a starter electrodeextending inside said cathode, and a second grid interposed between saidstarter electrode and said first grid.

7. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode surrounded by a sleeve ofinsulating material, a first grid substantially covering the end of saidinsulating sleeve and shielding said anode, a starter electrodeextending inside said cathode, said starter electrode comprising a Ushaped Wire, and a second grid interposed between said starter electrodeand said first grid.

8. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode surrounded by a sleeve ofinsulating material, a cup-shaped grid surrounding said insulatingsleeve and said anode, a starter electrode extending inside saidcathode, said starter electrode comprising a U-shaped wire, and acup-shaped grid between said starter electrode and said first-mentionedcup-shaped grid.

9. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode surrounded by a sleeve ofinsulating material, a cup-shaped grid surrounding said insulatingsleeve and said anode, a starter electrode extending inside saidcathode, said starter electrode comprising a U-shaped wire, and a planargrid between said starter electrode and said cup-shaped grid.

10. An electron discharge device comprising an envelope containing agaseous medium, a hollow cathode, an anode, a first grid substantiallyshielding said anode from said cathode, a control grid positionedbetween said first grid and said anode, and a grid positioned adjacentsaid cathode and adapted to maintain a keep-alive discharge therewith.

11. A gaseous discharge device comprising a large area main cathode, anelectrode adjacent said. main cathode, means biasing said electrode andcathode to maintain a keep alive discharge therebetween, a small areaanode opposite said cathode and defining a gap therewith, means biasingsaid anode relative to said cathode at a potential above the sustainingpotential of said gap but insufficient in itself to eifect breakdown ofthe gap, a control electrode adjacent said anode in said gap, and meansbiasing said control electrode for effecting the controlled injection ofelectric carriers from said discharge into said gap.

12. A gaseous discharge device comprising a large area cold cathode, asmall area main anode opposite said cathode and defining a main gaptherewith, an auxiliary anode in said gap adjacent said cathode anddefining a keep alive gap therewith, and a large area control electrodein said main gap adjacent said main anode.

References Cited in the file of this patent UNITED STATES PATENTS1,877,607 Skellett Sept. 13, 1932 1,939,063 Knowles Dec. 12, 19331,986,397 Hund Jan. 1, 1935 2,015,498 Schroter et a1. Sept. 24, 19352,435,246 Stutsman Feb. 3, 1948 2,479,274 Simons Aug. 16, 1949 2,481,365Stutsman Sept. 6, 1949 2,491,425 Stutsman Dec. 13, 1949 2,541,335 OarneFeb. 13, 1951

